1. Field of the Invention
The present invention relates generally to message passing, and more particularly to message passing in multimedia systems.
2. Description of Related Art
The need for greater processing power in multimedia systems along with power consumption constraints has led to a new era of parallel computing or multi-core designs. One feature of parallel computer architecture is its inter-process communication (IPC). Message passing is one of the methods used for IPC. A prior art message passing system consists of FIFOs wherein the message buffers are written by one microprocessor (a “producer”) and read by another microprocessor (a “consumer”) respectively. FIGS. 1A and 1B illustrate a prior art message passing system consisting of a simple FIFO (First-In-First-Out). A message queue may have a start pointer and an end pointer, and the queue length therebetween is the message queue length. A write pointer and a read pointer are maintained and used to indicate a portion for previously read data, a portion for unread data, and a portion available for new data. When a producer writes a message to the queue, the write pointer is incremented, and when a consumer reads a message from the queue, the read pointer is incremented. FIG. 1A illustrates an un-wrapped state of operation wherein the write pointer is less than the read pointer, and FIG. 1B illustrates a wrapped state of operation in which the previously read data and the data to be written share the same portion.
In the system shown in FIGS. 1A and 1B, a message can be consumed by one consumer, since once a message is consumed, the read pointer in the FIFO increments, and the message is removed from the FIFO. To have a message from a producer be read by multiple consumers, the message has to be written in multiple queues, which considerably increases memory footprint. In addition, multiple FIFOs have to be read.
Another problem of the prior art system shown in FIGS. 1A and 1B is its inefficiency in system latency. The FIFO treats all messages the same way according to the first in first out logic. Since sub-computations involved in different applications in a multimedia system may have variable latencies, different incoming messages may consume varying amounts of time to process, thus leading to unpredictable response time. However, real time responsiveness is important in multimedia applications.